Retired U.S. Marine Corps Gen. James Mattis explains that America cannot be seen as an automatic inheritance; you have to work for it and fight for it, in this clip from Uncommon Knowledge. Photo: AP

This transcript has been automatically generated and may not be 100% accurate.

... what would you say your kid in your circumstances over Washington State or maybe somebody here at Stanford University is considering the ROTC program ... about why ... the Korea or in the armed forces of the United States ... would still be a worthwhile to spend ... twenty or ... more years of your life ... why I think what you want ... one could do is explain that there comes a point your life when you wanna know the use or for a profession this world ... Tanner said gravestone of the Cypress Hills Cemetery in New York ... that day that we all love when we were kids going up in the sparkling baseball and we all wanna be Jackie Robinson ... if you go to Des Graham today it has a life is not important except in the impacted as on other lives ... that would be eroded on up to ... what ... I think that when you look at this experiment we call America we should not look of the people who founded it as if they had an easy time of it ... and they are now just faces on dollar bills ... we should not look this is something that is just automatically are inherent to ... then after work for a ... time when a fight for it ... because we might've been born here most of us ... by complete accident ... good fortune we lived here by choice ... we have an obligation to turn this free country over ... young men and women with the same freedoms that we got when we grew up ... and if you wanna be part of something to keep you from Stoughton in a ... psychiatry scare when you're forty five and what you do it to life ... you can't go wrong than going up and going up the Army the Navy Air Force Coast Guard Marine Corps ... this pattern for years ... and feel like a good stick around for longer ... frankly I dislike many of the job done ahead ... of the meringue ... I did a minefield of ... twenty one year old infantry lieutenant ... but I also grew to love being around guys to call ... willingly into minefields long side ... and so I idea I just recommended if you wanna get for from the will live avenues of life and protester shelf ... in the toughest circumstances alongside the best people in the world ... will never regret serve in the U S health care ...